1. Field of the Invention
This invention relates to an improved process for recovering gamma-butyrolactone (.gamma.-butyrolactone) from a mixture of heavy organics by means of azeotropic distillation.
2. Description of the Related Art
.gamma.-Butyrolactone (GBL) is a commodity of commerce useful in various applications such as a chemical intermediate, e.g., in the preparation of butyric compounds and polyvinylpyrrolidone, a solvent for various polymers, e.g., acrylate and styrene polymers, and in specialty products such as paint removers, textile assistants and drilling oils.
In a number of commercial processes resulting in the synthesis of GBL, e.g., the liquid phase oxidation of butane with molecular oxygen and the reaction of acetylene and formaldehyde using Reppe chemistry, the GBL is obtained in admixture with other relatively heavy, i.e., high boiling organic compounds, several of which have boiling points very close to GBL, e.g., the methyl-.gamma.-butyrolactones (MeGBL's). In view of this, it is difficult to recover GBL in sufficiently high purity from these other heavy organics without incurring prohibitively high energy and equipment costs so that in many instances, mixtures of heavy organics containing a relatively high percentage of GBL are burned for fuel rather than treated to recover the GBL. Thus, any expedient which is effective in rendering the economic recovery of GBL in high purity from mixtures with heavy organics, would be very desirable.
U.S. Pat. No. 2,875,213 issued Feb. 24, 1959 to Ulvild et al., discloses the recovery of GBL from a distillation fraction of the product of liquid phase oxidation of n-butane, comprising a major proportion of GBL and a minor proportion of glycol esters having boiling points close to that of GBL, by solvent extraction with a dual solvent of water and a liquid aliphatic hydrocarbon, e.g., n-hexane, to obtain aqueous and hydrocarbon phases, and obtaining GBL of high purity from the aqueous phase by distillation.
U.S. Pat. No. 4,851,085, issued Jul. 25, 1989 to De Thomas, discloses a process of treating GBL of at least 95% purity with a strong acid, e.g., a mineral acid or acidic ion exchange resin, to remove color forming impurities for product stabilization.
U.S. Pat. No. 5,319,111 issued Jun. 7, 1994 to Zimmermann et al. teaches a process for the preparation of tetrahydrofuran and GBL from the product of the hydrogenation of maleic acid, succinic acid, maleic anhydride, succinic anhydride and/or fumaric acid, by treating the crude hydrogenation product with a protic acid, e.g., a mineral acid or cation exchange resin, and isolating pure tetrafuran and GBL from the reaction mixture by distillation.